The present invention relates to a power system, and more particularly to the control of electric loads during a generator failure in a multi-generator system.
A power system for a vehicle typically includes two or more generators for redundancy. When one of the generators fails it is necessary to switch vital equipment that was supplied by the failed generator to a working generator. In order to prevent the remaining generator(s) from being overloaded when the additional loads are connected, it is necessary to disconnect, or shed, some of the lower priority loads before other equipment loads are transferred.
One known power system includes a #1 generator associated with a #1 primary bus and a #1 monitor bus. A #2 generator is provided to power a #2 primary bus and a #2 monitor bus. The primary buses are typically used to power higher priority and flight critical equipment, and the monitor buses provide power to lower priority auxiliary and peripheral equipment. Should one of the generators fail, for example the #1 generator, the #1 and #2 monitor buses are automatically de-energized, and the #2 primary bus, and the #1 primary bus are powered from the #2 generator. Equipment must therefore be pre-categorized into mission critical (primary bus) and less-critical (monitor bus) categories.
Entire busses may be subject to cut-off, typically by an electromechanical relay, in cases of severe generating capacity loss. Such automatic, xe2x80x9cblockxe2x80x9d reduction in load protects the vehicle from having the remaining generator overloaded and subsequently cut-off.
Disadvantageously, a block reduction approach requires that the mix of critical and less-critical loads be determined at the time the vehicle is designed and hard-wired into the power system. This categorization may be based on a predefined set of assumptions and generator conditions which may unnecessarily de-energize particular equipment upon generator degradation and thus may not allow for current mission circumstances.
Accordingly, it is desirable to provide a power system which will quickly appraise a vehicle crew of the current generator capacity and power margins such that the impact of additional loads is identifiable. It is further desirable to provide a power system which allows selective alteration and application of equipment loads in response to changing circumstances.
The vehicle power system according to the present invention includes a multiple of electrical generators which provide power for vehicle electrical systems or loads through an electrical load management center (ELMC). A general purpose processor set (GPPS) is responsive to operator generated commands, vehicle sensors, stored subroutines and program algorithms to instruct the ELMC such that the power supplied to each electrical load may be individually controlled by an associated solid state power controller (SSPC).
The GPPS monitors various vehicle system parameters via a sensor interface (SI) which communicates with each generator. Sensors identify and monitor a multiple of generator operating parameters such as the temperature and pressure of a generator cooling fluid and output voltage and output current. The GPPS can then determine the total load actually being drawn from the generators in terms of kilowatts by multiplying the output voltage by the output current. The GPPS also relates the generator readings from the SI to a generator-rating algorithm stored in the database to determine an allowable load which may be placed on the system. Preferably, the generator-rating algorithm is stored as a look-up table which includes a relationship that rates each generator""s capacity as a dependent function of its prevailing cooling fluid characteristics.
A display communicates with the GPPS to present an electrical system status screen to the vehicle crew such that the crew is constantly made aware of the prevailing electrical power conditions in a rapid and efficient manner.
During a drastically reduced electrical supply situation, loads are shed to avoid overloading the remaining operating generator(s). Certain electrical loads are automatically disconnected by deactivating a particular SSPC through GPPS commands to the ELMC via a predefined load shed priority list.
Once electrical loads are disconnected via the predefined load shed priority list the crew may desire to reactivate particular systems for the current mission circumstances. The present invention provides for the reactivation of particular loads which were previously shed according to the predefined load shed priority list. A load recovery screen preferably includes a columnar format having all loads which may be recovered in a TO RECOVER column and all loads which may be shed in a WILL SHED column.
As particular systems are selected on the load recovery screen, a sum of the total loads slated for recovery and a sum of the total loads slated to be shed are indicated at the bottom of each column. When the total loads slated to be shed is equal or greater than the total loads slated for recovery, a recover load selector is activated. By activating the recover load selector, the selections are activated to reconfigure the complement of powered loads as directed by the load recovery screen. In response to the load recovery screen, the GPPS sends instructions to the ELMC such that each selected electrical load is individually actuated or deactivated by remotely controlling the particular SSPC associated with the selected electrical load. Thus, the system is reconfigured to timely provide the crew with the selected operational systems independent of the predefined load shed priority list.